1. Field of the Invention
The present invention relates to a magnetic element comprising a coil wound onto a magnetic core, and more specifically relates to an inductor component such as an inductor and transformer and the like which is used in various types of electronic equipment and in electric power sources, for reducing core loss using DC bias.
2. Description of the Related Art
In recent years, various types of electronic equipment are being reduced in size and weight. Accordingly, the relative volume percentage of the electric power source units of such electronic equipment has tended to increase with respect to the overall volume of the electronic equipment. This is due to the fact that, while various types of circuits are being contained in LSIs, reduction of size of magnetic parts such as inductors and transformers which are indispensable circuit components for electric power source units is difficult. Hence, various methods have been attempted for reducing electrical power source units in size and weight.
Magnetic elements such as inductors and transformers (which will hereafter be collectively referred to as xe2x80x9cinductor componentsxe2x80x9d) can be effectively reduced in size and weight by reducing the volume of magnetic cores formed of magnetic materials.
Generally, reduction in the size of cores facilitates magnetic saturation of the magnetic core, which is problematic in that the current value which can be handled as a power source is reduced.
As a means for solving this problem, an art is known wherein a part of a magnetic core contains magnetic gaps, thereby increasing the magnetic resistance of the magnetic core and preventing reduction in current value. However, the fact that the magnetic inductance of such magnetic parts deteriorates is also known.
Various methods are known for preventing deterioration of magnetic inductance of inductor components, such as a method of disposing a permanent magnet near a gap (hereafter referred to as xe2x80x9cprior art 1xe2x80x9d), a method for bridging a gap using a permanent magnet (see Japanese Unexamined Utility Model Publication No. 54-152957), or a method for connecting a gap by mounting a permanent magnet thereto (see Japanese Unexamined Patent Application Publication No. 1-169905, hereafter referred to as xe2x80x9cprior art 2xe2x80x9d), thereby applying DC bias, and increasing the change in magnetic flux density, so as to increase processing electric power.
Prior art 2 describes a technique relating to the structure of a magnetic core using a permanent magnet for generating magnetic bias. This technique involves a method inwhich DC magnetic bias is applied to a magnetic core using a permanent magnet, consequently increasing the number of lines of magnetic force capable of permeating the magnetic gap.
However, in the event that a metal magnetic material having a high-saturation magnetic flux density (B), e.g., silicone steel, permalloy, amorphous material, is used as the magnetic core for the choke coil according to prior art 1, the permanent magnet formed of sintered material, e.g., rare-earth magnets such as Smxe2x80x94Co or Ndxe2x80x94Fexe2x80x94B or the like, generate heat from eddy current loss due to the high magnetic flux density of the magnetic core even if positioned outside the path of magnetism, so the properties of the permanent magnet deteriorate.
Also, with the configuration of the magnetic core of the inductor according to prior art 2, magnetic fluxes from a coil wound on a magnetic core pass through the permanent magnet within the magnetic gap, causing a problem of demagnetizing the permanent magnet. Also, there has been the problem in that the smaller the form of the permanent magnet inserted in the magnetic gap is, the greater the effects of demagnetizing due to external factors is.
Accordingly, it is an object of the present invention to provide an inductor component in which few restrictions exist with regard to the form of the positioned permanent magnet, generation of heat of the permanent magnet due to the magnetic flux from the coil wound on the magnetic core is suppressed, and in which properties do not deteriorate.
According to the present invention, there is provided an inductor component which comprises a magnetic core comprising at least one gap, an excitation coil disposed on the magnetic core so as to form a magnetic path on the magnetic core, at least one permanent magnet disposed near the at least one gap, and at least one first soft magnetic material piece disposed between the at least one permanent magnet and the magnetic core, wherein the first soft magnetic material piece is formed of a soft magnetic material which has a smaller permeability and less eddy current loss than the magnetic core.